The present invention relates to a transmission apparatus of video information, a transmission system of video information and a transmission method of video information.
In recent years the application field of computers has widened. In it a computer wherein a part (referred to as “first terminal apparatus”) including a CPU (central processing unit) or the like, and a part (referred to as “second terminal apparatus”) including a display part for video (or display part and input part) are separated is in demand by the market.
FIG. 3 is a conceptual diagram of a computer which has a first terminal apparatus and a second terminal apparatus.
In FIG. 3, the first terminal apparatus which includes a CPU is denoted as 301, the second terminal apparatus which includes a display part and a pen input part is denoted as 302, a conventional PC (abbreviation of personal computer which has a CPU and a display part) is denoted as 303, a docking station is denoted as 304, a keyboard is denoted as 305 and a display part is denoted as 306. The first terminal apparatus 301 has a CPU 311 and a wireless communication part 312. The second terminal apparatus 302 has a display and pen input part 321 and a wireless communication part 323. The user can input instructions to the computer by touching a pen 322 to the display and pen input part 321.
Video information generated in the CPU 311 of the first terminal apparatus 301 is transmitted from the wireless communication part 312. The wireless communication part 323 of the second terminal apparatus 302 receives the video information and transmits it to the display and pen input part 321. The display and pen input part 321 displays the inputted video information.
When the user inputs instruction for the computer to the display and pen input part 321 of the second terminal apparatus with the pen 322, this instruction information is transmitted from the wireless communication part 323. The wireless communication part 312 of the first terminal apparatus 301 inputs this instruction information, and transmits it to the CPU 311. The CPU 311 inputs instruction information and processes information in accordance with the instruction information.
Generally the user only utilizes the first terminal apparatus 301 and the second terminal apparatus 302. The user can move freely by carrying around the second terminal apparatus 302 which is light and which does not have a connection cord.
The user connects the docking station 304 to the first terminal apparatus 301 and connects the keyboard 305 and the display part 306 to the docking station 304 and, thereby, can construct and utilize a computer system comprising the first terminal apparatus 301, the docking station 304, the keyboard 305 and the display part 306.
An optional wireless communication part 331 can be incorporated into the conventional PC 303. The video information generated by the CPU of the PC 303 is transmitted from the wireless communication part 331. The wireless communication part 323 of the second terminal apparatus 302 receives the video information and transmits it to the display and pen input part 321. The display and pen input part 321 displays the inputted video information.
When the user inputs instruction for the computer to the display and pen input part 321 of the second terminal apparatus with the pen 322, this instruction information is transmitted from the wireless communication part 323. The wireless communication part 331, which is incorporated into the conventional PC 303, inputs this instruction information and transmits it to the CPU. The CPU of the conventional PC 303 inputs the instruction information and processes information in accordance with the instruction information.
In this manner, the user can utilize a conventional PC as the first terminal apparatus 301.
FIG. 15 is a block diagram, (mainly showing a transmission apparatus for video information and a transmission system for video information included in the computer) of a conventional computer which has a first terminal apparatus and a second terminal apparatus. The conventional computer of FIG. 15 includes an video information transmission apparatus which transmits video information from the first terminal apparatus to the second terminal apparatus.
In FIG. 15, the first terminal apparatus is denoted as 1501, the second terminal apparatus is denoted as 1502, a display (display part) is denoted as 1503 and a wire connecting the first terminal apparatus 1501 with the second terminal apparatus 1502 is denoted as 1504.
The first terminal apparatus 1501 has a CPU 1511, a video graphics control part 1513, an LCD driving part 1515 (liquid crystal display driving part), a liquid crystal display 1516 and a communication board 1514. Though indispensable for a computer, a ROM, a RAM and the like, which do not relate directly to the present invention, are omitted in the description.
The CPU 1511, the video graphics control part 1513 and the communication board 1514 are connected to each other via a PCI bus 1512.
The video graphics control part 1513 has a CPU 1521, an input/output part 1522, a RAM 1523, a VRAM 1524, a write in/read out address register 1525, a read out address register 1526, a clock generator 1527 and a parallel/serial conversion part 1528.
The CPU 1521, the input/output part 1522, the RAM 1523, the VRAM 1524, the write in/read out address register 1525 and the like are connected to each other via an internal bus 1529.
The CPU 1511 transmits video change instructions which are described in a software language (such as DirectX (registered trademark of Microsoft Corporation)) to the video graphics control part 1513 and the communication board 1514 via the PCI bus 1512.
The input/output part 1522 of the video graphics control part 1513 transmits the inputted video change instructions which are described in a software language to the CPU 1521 via the internal bus 1529.
The CPU 1521 converts the video change instructions which are described in a software language (program arranged on the Application Programming Interface of the OS of this computer) into the level information (for example, information concerning the value to which the value of any address of the VRAM is changed) of each pixel at the hardware level by utilizing an video information decoder 1541. The RAM 1523 is a scratch region at the time when the level information of each pixel is generated, by utilizing the video information decoder 1541. The VRAM 1524 is a dual port RAM for video display which has a port that can randomly access an arbitrary address so as to carry out write in and read out (address is designated by a write in/read out address register 1525) and a port that can read out data of each address at high speed and in a constant order (address is designated by a read out address register 1526). The level information (level information of each of the sub-pixels, RGB), attribute data and the like are stored in the VRAM 1524.
The CPU 1521 and the like set an address in the write in/read out address register 1525. Information is written into this address through the internal bus 1529 and information is read out from this address through the internal bus 1529.
The clock generator 1527 sets a read out address register 1526. The set value of the address register 1526 is generally incremented at an extremely high rate. The information of the address designated by the address register 1526 is read out and is forwarded to the parallel/serial conversion part 1528. The parallel/serial conversion part 1528 converts the inputted information of each address (level information of each pixel) into serial data, which are then outputted.
An output signal from the parallel/serial conversion part 1528 is transmitted to an LCD driving part 1515 and is converted to a signal for driving an LCD (liquid crystal display). The LCD driving part 1515 drives the liquid crystal display 1516. The liquid crystal display 1516 displays video.
In addition, the output signal from the parallel/serial conversion part 1528 is transmitted to the external display 1503. The display 1503 displays video.
The communication board 1514 receives the video change instructions which are described in a software language and which are transmitted through the PCI bus 1512 (outputted by the CPU 1511). The communication board 1514 transmits the video change instructions which are described in a software language to the second terminal apparatus 1502 through the connecting wire 1504.
The communication board 1531 of the second terminal apparatus 1502 transmits the received video change instructions which are described in a software language to the video graphics control part 1532. The video graphics control parts 1532 and 1513 have the same configuration. The video graphics control part 1532 generates and outputs the display data of each pixel based on the video change instructions which are described in a software language. The display 1533 displays video by driving each pixel in accordance with the display data.
In a conventional computer which has a first terminal apparatus and a second terminal apparatus, however, information flow between the first terminal apparatus and the second terminal apparatus is carried out with video change instructions which are described in a software language. Therefore, data cannot be transmitted or received between the first terminal apparatus and the second terminal apparatus in which different OSs are installed. In particular, the user who has a plurality of first terminal apparatus in which plural and different OSs are installed must utilize, through precise differentiation, a first terminal apparatus and a second terminal apparatus in which a first OS is installed as well as a first terminal apparatus and a second terminal apparatus in which a second OS is installed, and, in this regard, mistakes may easily occur. For example, the case wherein the user brings the first terminal apparatus in which the first OS is installed and the second terminal apparatus in which the second OS is installed on a distant trip, results in the apparatus being unusable. Therefore, a data transmission system between a first terminal apparatus and a second terminal apparatus that does not depend on an OS is requested by users who have a plurality of first terminal apparatus in which plural and different OSs are installed.
There is also the idea of transmitting the output signal from the parallel/serial conversion part 1528 to the second terminal apparatus 1502 without change. However, in the case that a full color display with RGB consisting, respectively, of 8 bits is implemented on a UXGA screen (1600×1200 pixels), the output signal of the parallel/serial conversion part exceeds 46 Mbps. It is extremely difficult to transmit data at such a high rate in a wireless manner.
The present invention has the purpose of providing a transmission apparatus for video information, a transmission system for video information and a transmission method for video information which enable wireless transmission of video information at a low rate regardless of OS.